1. Field of Art
The disclosure generally relates to the field of multimedia switching, receiving and repeating.
2. Description of the Related Art
A multimedia interface system transports multimedia signals from a multimedia source to a multimedia sink. Examples of a multimedia source include a computer, a DVD player, a set-top box, a game consoles or another device producing multimedia output. Examples of a multimedia sink include a monitor, a television, an audio/visual (A/V) receiver or other device which receives and presents video and/or audio. When a system includes more than one multimedia source, the system switches between different multimedia sources to modify the multimedia source providing data to the multimedia sink. Between the multimedia source and the multimedia sink, there is a multimedia link including a transmitter, a switch and a receiver. Examples of multimedia links in such a multimedia switching system are DISPLAYPORT, HDMI and DVI.
Often, the multimedia link is protected by a digital content protection scheme, e.g., HDCP. Before sending content-protected data, the transmitting device initiates an authentication process to confirm that the receiver is authorized to receive the data. Once the receiver has been authenticated, the transmitter encrypts the data stream to prevent eavesdropping and sends the encrypted data stream to the receiver. Hence, when switching to a second multimedia source, the second multimedia source initially starts content protection procedures before sending multimedia content to the multimedia sink. However, the authentication confirming that the receiver is authorized to receive data from the second multimedia source is time consuming. Normally, several seconds are required for the second multimedia source to authenticate that the multimedia sink is permitted to receive multimedia data from the second multimedia source. After the authentication process is completed, the second multimedia source begins transmitting content to the multimedia sink; however, the delay caused by authentication is disruptive for many content viewers.
Conventional techniques for reducing the delay caused by authorization of the multimedia sink by a multimedia source require a dedicated receiver and content decryption block for each input port of a multimedia switch. A logic switch selects an input from multiple input ports for communication to the multimedia sink. Hence, input ports are continuously connected to various multimedia sources so that the multimedia sink is authenticated to receive data from the various multimedia sources. This continuous connection and authorization allows switching from a first input port to a second input port without disrupting communication of multimedia content to the multimedia sink for display.
While this conventional method reduces switching delay by removing the need for re-authentication after switching to a new multimedia source, drawbacks remain. In particular, each port completely decodes and decrypts received data, increasing system cost and computing resources.
An alternative configuration reducing the delay in switching between multimedia sources uses two receiver cores. A main receiver core is dedicated for the currently selected port and receives multimedia content from a multimedia source coupled to the selected port. A roving receiver core receives data from different multimedia sources coupled to different background ports which are not selected. The background port providing data to the roving receiver core rotates over time, so that at different time intervals the roving receiver core receives data from different non-selected background ports.
In such an alternate configuration, each input port is an HDMI input port coupled to a high-bandwidth digital content protection (HDCP) engine. The HDCP engine coupled to the selected input port receives HDCP encryption status signaling from the main receiver core. HDCP engines coupled to the background, or non-selected, ports receive HDCP encryption status signaling from the roving receiver core. When the HDCP engine for a background port is connected to the roving receiver core, the HDCP engine for the background port uses HDCP encryption status signaling from the roving receiver core. When the HDCP engine for a background port is not connected to the roving receiver, the HDCP engine operates in an open-loop mode using assumed HDCP encryption status signaling. However, when an HDCP engine operates in an open-loop mode, the HDCP engine may miss HDCP encryption data indicating a status change. Additionally, this configuration is limited to application in an HDMI system with HDCP content protection.